Scientists crank up the voltage, create better dark-matter search

Sep 30, 2013

The CDMS experiment uses particle detectors made of germanium and silicon crystals.

Scientists on the Cryogenic Dark Matter Search have set the strongest limits in the world for the detection of a light dark-matter particle with a mass below 6 billion electronvolts, or about six times the mass of a proton.

The composition of dark matter, which accounts for more than 80 percent of all matter in the universe, could be as complicated as the makeup of ordinary matter. In the past, many experiments have focused on searching for dark-matter particles that are heavy. But recent experimental results and new theoretical models have provoked a strong interest in the search for light dark-matter particles.

The CDMS collaboration, which includes scientists from DOE's Fermilab, SLAC and Pacific Northwest national laboratories, looks for dark-matter particles using particle detectors made of germanium and silicon crystals cooled close to absolute zero. If a dark-matter particle traverses a detector and knocks against the nucleus of an atom, the interaction will release a small amount of heat and electric charge, which the experiment's sensitive.

The lighter the particle administering this kick, the smaller the amount of heat and charge released. That makes light dark-matter particles particularly hard to find.

Pushing the boundaries of detector technology, CDMS scientists have found a way to amplify the tiny signal that such light particles would release by applying a large voltage across a crystal. This gives the scientists a much closer look at the mass range where light dark-matter particles could exist.
The modified detector is not well suited for looking for heavy dark-matter particles, whose larger signals would saturate the experiment's electronics. CDMS scientists will continue their quest for both light and heavy dark-matterparticles by operating their detectors in different search modes. They plan to include the high-voltage technology in a proposed, large detector to be placed more than a mile underground at the SNOLAB in Canada.

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User comments : 10

Scientists on the Cryogenic Dark Matter Search have set the strongest limits in the world for the detection of a light dark-matter particle with a mass below 6 billion electronvolts, or about six times the mass of a proton.

The composition of dark matter, which accounts for more than 80 percent of all matter in the universe, could be as complicated as the makeup of ordinary matter….

It seems that this is not really a light dark-matter particle comparing to a neutrino; how about this truly lighter one (which is a continuous medium form instead of a particle) that fill all the huge empty vacuum space of the universe ….http://www.vacuum...14〈=en

Since "dark" matter is most of the universe by a large margin, why not just call it matter? The leftover stuff that we are made of etc.,

Because it's matter that doesn't interact electromagnetically. Light, being an electromagnetic phenomenon, is pretty much our only source of observations about the cosmos at large. Now, because of that instrumentation bias (we don't really have much choice in the matter though), the matter we've known about has either emitted light because it's hot or reflected/scattered light, or absorbed it.

Now there's a lot of mass we've observed that is disproportionate to the amount of light-interacting matter we've observed. So the remaining stuff is "matter-that-doesn't-interact-electromagnetically." We're aware of one type of "matter-that-doesn't-interact-electromagnetically" already, neutrinos. But they're so low massed that they don't tend to clump around galaxies like this other stuff, so we figure there's some other stuff like neutrinos yet there

@ vlaaing peerd: The cold dark matter paradigm has many problems on the "small" scale of galaxies and galaxy groups. This is very well known, very well studied and very unsolved; attempts for solutions look more like epicycles. Nevertheless this is hardly mentioned by proponents of the theory, for instance, not in the Planck papers and neither in the above press release nor in the paper on which it is based.Even worse is the location of satellites of our Galaxy: the research group of Kroupa in Bonn keeps repeating that its actual structure, they appear to lie in a plane, can not be explained from cold dark matter and that the standard model of cosmology is falsified. Also Andromeda has such a plane. This is a problem for theorists, the Galaxy is OK, I couldn't live in another one.

DM is nothing more than a skeleton of electrodynamically active regular matter, a baryonic cold skeleton so to speak.

We know from nucleosynthesis that the majority is non-baryonic. That is also borne out by the Bullet Cluster. In this image, the location of the DM (from lensing) is blue while the hot baryonic matter is shown in red: